sedimentary

Yellow Chert (Yellow Jasper)

Silicon Dioxide (SiO2)

Hardness: 6.5-7. Color: Yellow to brownish-yellow. Luster: Waxy to dull. Crystal Structure: Microcrystalline/Cryptocrystalline (Trigonal). Cleavage: None, conchoidal fracture. Specific Gravity: 2.58-2.91.

Hardness: 6
Color: Yellow to brownish-yellow
Luster: Waxy to dull

Identified July 1, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed as a result of the accumulation of microscopic silica fossils (like radiolaria or diatoms) or chemical precipitation from silica-rich fluids in sedimentary basins. Often found in limestone or dolomite formations.

Uses & applications

Historically used for stone tools due to sharp edges when fractured. Currently used for lapidary work, jewelry (cabochons), tumbling, and aggregate in construction.

Geological facts

Yellow chert is often referred to as Yellow Jasper when it is opaque and highly aesthetic. Because it is highly resistant to weathering, it often survives as stream-worn pebbles long after the surrounding rock has eroded.

Field identification & locations

Identify by its waxy luster, conchoidal fracture (smooth, curved breaks), and extreme hardness (cannot be scratched by a steel knife). Commonly found in gravel pits, riverbeds, and beach deposits.

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Sandstone or Siltstone

Arenite (if sandstone)

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Cone-in-cone structure (Limestone)

Cone-in-cone structure (Secondary Sedimentary Structure)

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Sandstone Grain

Clastic Sedimentary Rock Grain (SiO2 dominated)

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Chert Breccia

Brecciated Chert (Microcrystalline Silica)

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Shale or Slaty Mudstone

Argillaceous sedimentary rock

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Sandstone

Arenite (primarily SiO2)

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